What is the Janka Wood Hardness Scale ?

When choosing the right type of hardwood to install in a residential property or a commercial office space, various factors will come into play. Clients often have very clear preferences regarding color, durability, ease of maintenance, and of course, pricing. But professionals in the flooring industry know that there are other factors that clients might not be aware of, that play a big part in the decision-making process. Hardness is one of those factors. But what does it mean, exactly? 

Hardness is a crucial factor that you need to consider when working with a client to choose the right type of hardwood for their specific needs. Luckily, flooring professionals know that there is an industry standard test dubbed the Janka hardness test, which measures hardness in different types of hardwood. If durability and wear and tear are major deciding factors in your project, you can present your client with the best options from the Janka hardness rating list and pick the best hardwood for the space together. 

Why is wood hardness important?

The Janka hardness scale was created by Austrian-born American researcher Gabriel Janka, who realized that certain types of wood were harder, or softer, than others, and that hardness might be a crucial factor that impacts hardwood durability over time. He then came up with a way of measuring hardness in hardwood planks, and then started ranking the different types of domestic and exotic hardwoods according to their ‘hardness,’ or toughness. 

Basically, types of wood that are harder will be more resistant to wear and tear, and will prove more durable over time, so they’re good choices for high-traffic areas like offices or retail stores. Softer hardwoods are more prone to denting, scratching, or damage, either during the installation process or during normal daily use. Hardness is thus important because it could influence the durability of the hardwood planks, the maintenance and upkeep required, and how often the planks will need to be repaired or replaced. Additionally, the Janka rating will tell you how well the wood will withstand damage from handling, nailing, cleaning, sawing, or drilling. 

However, the Janka scale is not absolute by any means, and one should keep in mind that all types of hardwood are quite durable and long-lasting, which is why they’re so sought-after, both by residential and commercial clients. You can install hardwood planks with a very high hardness rating, but if the wood is not right for the specific space or the environmental conditions, it won’t be as durable as a softer alternative. Hardness is only one factor that needs to be considered in the decision-making process, but definitely not the only one. 

How is hardness measured using the Janka rating?

The process by which hardwood is awarded a Janka hardness rating involves embedding a steel ball that is 0.444 inches / 11.29 millimeters in diameter halfway into the surface of a hardwood plank. The hardness rating of the wood is determined by the force required to push the steel ball into the wood. It’s measured in pounds-force (lbf) in the U.S., in kilograms-force (kgf) in Europe, and in newtons (N) in Australia. For instance, Cherry wood has a Janka rating of 995 lbf, which means that it took 995 pounds of force to embed the steel ball into the Cherry wood plank. 

The Janka rating only measures the hardness of the wood’s ‘face,’ and not its edges or sides. This is mostly because any force applied to the wood during the installation process or during daily use will be to its face, and not to its sides. 

For hardwood floors, the Janka test will require a 50mm by 150mm sample with a thickness of at least 6 to 8 millimeters. When testing the hardness in lumber form, wood from the tree trunk will always be used, also known as the heartwood, and it’s important that the sample chosen for the test is clear of knots and has a 12% moisture content.

What is a ‘good’ Janka rating?

Hardwood flooring is usually durable and very resistant to wear and tear, scratching, denting, or warping during the course of its lifetime. Still, a Janka rating around 1,000-1,200 lbf is considered ideal, and the industry mean. This includes woods like Black Walnut, Teak, Larch, Red Oak, and Ash, for example. However, there are other factors to keep in mind, like humidity and traffic. If the space is subjected to heavy traffic on a daily basis, either in an office space or a household with pets and children, then a hardwood with a high Janka rating is preferable. If the project involves a low-traffic area like a home library or home office, then a lower Janka rating is more than acceptable. 

Which types of hardwood boast the highest Janka rating?

There are hundreds of wood varieties in the world, and the hardest ones are found in Australia, Brazil, Argentina, Paraguay, and other parts of South America. In North America, some of the toughest types of hardwood include Hickory, Hard Maple, White Oak, Red Oak, and Beech. Chestnut, Larch, Douglas Fir, and Silver Maple are some of the types of wood with a low Janka hardness rating. All in all, hardness is an essential factor to consider when choosing the right type of hardwood for your project, but as always, you need to consider every other factor as well to make the best choice for your client’s needs.